Ionic liquid assisted fabrication of cellulose-based conductive films for Li-ion battery

An imidazolium-based ionic liquid, 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP) was used to dispense graphene nanoplates (GN) and multiwalled carbon nanotubes (MWCNTs) as well as dissolve cellulose for fabricating composite conductive films. The effects of GN, MWCNTs, and cellulose mass ratios on the electrical conductivity and morphology of the films were investigated. The interaction between GN, MWCNTs, and cellulose was analyzed by SEM, X-ray diffraction (XRD), TGA, and Raman spectroscopy. The results indicate that [Emim]DEP plays a vital and irreplaceable role in GN and MWCNTs dispersion, cellulose dissolution, and porous formation during the regeneration and drying processes. MWCNTs linked flaky GN and a hybrid structure was constructed elaborately to form a better conductive path and improve the conductivity as well as increase the film stability. For the XRD result, the carbonized GN-MWCNTs-cellulose films exhibited the graphitic peaks, showing that the films still retained the structure of carbon atoms or molecules. Besides, the maximum conductivity of carbonized GN-MWCNTs-cellulose (7:3:2) composite film was up to 9,009 S m⁻¹, due to the small carbon clusters formation and the high degree of graphitization. Further, the carbonized films were applied as anodes in Li-ion battery and showed good electrochemical performance. The best cyclic stability (i.e., discharge/charge capacity) of 438/429 mA h g⁻¹ and coulomb efficiency of 50.2% were obtained. This novel and sustainable design is a promising approach to obtain cellulose-based conductive films and anodes for Li-ion battery applications.     

Ionic conductivity of oxides based on Li4SiO4

Lithium orthosilicate, Li₄SiO₄, and its solid solutions are a new group of solids of high ionic conductivity. Either Li or Si may be at least partially replaced by several other di-, tri- or tetra-valent cations. Highest conductivities were found for solid solutions with Si partially replaced by Ti; typical values were 10^?3 to 10^?4 Ω^?1 cm^?1 at 300°C rising toc. l Ω^?1 cm^?1 by 700°C. The solid solutions are easy to prepare and are stable in air. Conductivities were measured on pressed cubes of powdered material using variable frequency a.c. methods. The conductivities of these Li₄SiO₄ solid solutions are compared with those of other known Li-conducting solids; Li₄SiO₄ solid solutions are probably the best all-round, polycrystalline Li-electrolytes yet found for temperatures abovec. 200°C.     

Synthesis of polysilane-acrylamide copolymers by photopolymerization and their application to polysilane-silica hybrid thin films

Various polysilane-acrylamide block copolymers have been prepared from photopolymerization of acrylamide-type monomers using poly(methylphenylsilane) (PMPS) as a macro-photo-radical initiator. The acrylamide block in the copolymers improved the hydrophilic property of PMPS. These PMPS-acrylamide block copolymers have been applied to formation of PMPS-silica hybrid thin films via sol-gel reaction. Homogeneous and transparent PMPS-silica hybrid thin films were obtained from a few PMPS-acrylamide block copolymers. It was found for these hybrid thin films based on hydrogen bonding formation between amide group and silanol group. The surface properties of hybrid thin films were evaluated by water contact angle measurement, scanning electron microscope (SEM), and atomic force microscope (AFM) images.     

Synthesis and electrical conductivity of films based on rare-earth oxides

A number of physicochemical properties of samples are investigated. Changes in the electrical resistance of films based on the yttrium, terbium, and praseodymium oxides in an air atmosphere and upon interaction with different gaseous media (ozone, argon, methanol, ethanol) are studied. The ranges of operating temperatures and the maximum relative sensitivity coefficients of the films under investigation are determined. Original Russian Text P.A. Tikhonov, M.V. Kalinina, P.V. Rastegaev, I.A. Drozdova, 2008, published in Fizika i Khimiya Stekla.     

Ionic liquid-mediated synthesis of crystalline CeO2 mesoporous films and their application in aerobic oxidation of benzyl alcohol

In this work, mesoporous CeO₂ crystalline film was prepared via calcining the solution of Ce(NO₃)₃ in ionic liquid (1-allyl-3-methylimidazolium chloride) containing cellulose. The as-prepared CeO₂ film was characterized by means of different techniques including X-ray diffraction, transmission electron microscopy equipped with energy dispersive X-ray spectroscopy, scanning electron microscopy and nitrogen sorption analysis. It was indicated that the as-prepared CeO₂ film was composed of numerous CeO₂ crystals with size of ～9 nm, which assembled with each other to form interconnected channels within the film. The BET specific surface area and the pore volume of the CeO₂ film were estimated to be 62 m²/g and 0.15 cm³/g, respectively, based on the N₂ sorption isotherms. Being used as a support, the CeO₂ film was loaded with Au nanoparticles of ～5 nm in size via the reduction of HAuCl₄ with NaBH₄ in aqueous solution. The as-synthesized Au/CeO₂ nanocomposite demonstrated a good catalytic activity for aerobic oxidation of benzyl alcohol.     

Ionic liquid mediated nano-composite polymer gel electrolyte for rechargeable battery application

ABSTRACT

Nano-composite polymer gel electrolytes (NPGEs) based on polymer poly(vinylidene fluoride-co-hexafluoropropylene) PVdF-HFP, ionic liquid, 1-butyl-3- methylimidazolium bis(trifluoromethanesulfonyl)imide BMIMTFSI, Li-salt along with the addition of SiO₂ nanoparticles have been synthesized and characterized by various techniques. Prepared NPGEs show high room temperature ionic conductivity (~10^?3 S/cm) and have a wide electrochemical window (ECW) (~3.3–3.5 V). The galvanostatic charge/discharge profile was studied by sandwiching best performing NPGEs between a LiFePO₄ cathode and lithium metal anode. The specific discharge capacity of the cell (Li/NPGE/LiFePO₄) room temperature at 0.1C rate is found to be 138 mAh/g.     

Ionic conductivity and interfacial properties of polymer electrolytes based on PEO and boroxine ring polymer

Blended polymer electrolytes based on poly(ethylene oxide) (PEO) and boroxine ring polymer (BP) solvated with lithium triflate were formulated and evaluated. Compared to PEO–salt polymer electrolyte, ionic conductivities of blended polymer electrolytes were two orders of magnitude higher in a low‐temperature range; as well, lithium transference numbers were increased to ～ 0.4. These were due to the increased mobility and anion trapping of boroxine rings. BP also exhibited the stabilizing effect on lithium–polymer electrolyte interface, and a reduced interfacial resistance between lithium metal and the polymer electrolyte was found with increasing of BP content. Polymer electrolytes based on PEO and BP are suitable for use in lithium secondary battery. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 17–21, 2002; DOI 10.1002/app.10090     

Ionic conductivity of chitosan membranes

Chitosan membranes with various degrees of deacetylation and different molecular weights (MW) were prepared by film casting with aqueous solutions of chitosan and acetic acid. Ultraviolet (UV) spectrometry and infrared (IR) spectrometry were used to determine the degree of deacetylation (DDA) of chitosan. The viscosity-average MW of chitosan was measured in an aqueous solvent system of 0.25 M CH₃COOH/0.25 M CH₃COONa. The intrinsic ionic conductivities of the hydrated chitosan membranes were investigated using impedance spectroscopy. It was found that the intrinsic ionic conductivity was as high as 10⁻⁴ S cm⁻¹ after hydration for 1 h. The tensile strength and breaking elongation of the membranes were evaluated according to standard ASTM methods. The crystallinity and swelling ratio of the membranes were examined. A tentative mechanism for the ionic conductivity of chitosan membranes is also suggested.     

NIR-shielding films based on PEDOT-PSS/polysiloxane and polysilsesquioxane hybrid

Near-infrared (NIR)-shielding films based on polysiloxane or polysilsesquioxanes and poly(3,4-ethylenedioxythiophene)-poly(4-styrene sulfonate) (PEDOT-PSS) were synthesized via a sol–gel reaction. Phase-separated mixtures of tetraethyl orthosilicate (TEOS) or methyltriethoxysilane (MTES) with an aqueous dispersion of PEDOT-PSS formed deep-blue homogeneously dispersed sols after stirring. Thin films were prepared by depositing the resulting homogeneously dispersed sols on a glass substrate by spin coating and heating. PEDOT-PSS/TEOS films maintained uniform flat surfaces after 10 coatings. MTES-based films exhibited mottled patterns with nonuniform surfaces. The 10-layer TEOS-based film has high NIR-shielding properties with moderately visible transmittance. NIR absorption by the PEDOT-PSS/TEOS hybrid suppresses air temperature elevation. The five-layer TEOS-based film showed similar NIR-shielding ability and slightly lower visible light transmittance compared with tin-doped indium oxide glass. The 10-layer TEOS-based film exhibited a 15.6% lower temperature rise than the uncoated glass substrate. Specifically, this is an environmentally friendly NIR-shielding material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48367.     

Ionic conductivity of single-crystal ferrierite

Ionic conduction in a single-crystal zeolite is reported for the first time. Sub-millimeter sized ferrierite is grown by an organothermal method, and the conduction of sodium cation is measured along [0 0 1] and [0 1 0] separately by a.c. impedance analysis. The main conduction along [0 0 1] is through ten-member ring channels, while that along [0 1 0] is through eight-member ring channels. The measurement at 673–873 K reveals that the conductivity along [0 1 0] is greater than along [0 0 1]. The activation energy along [0 1 0] (1.2 eV) was greater than that (0.84 eV) along [0 0 1]. These differences are discussed in view of the ferrierite framework structure.     

Low-temperature synthesis of multilayer graphene/amorphous carbon hybrid films and their potential application in solar cells

ABSTRACT: The effect of reaction temperature on the synthesis of graphitic thin film on nickel substrate was investigated in the range of 400 [DEGREE SIGN]C to 1,000 [DEGREE SIGN]C. Amorphous carbon (a-C) film was obtained at 400 [DEGREE SIGN]C on nickel foils by chemical vapor deposition; hybrid films of multilayer graphene (MLG) and a-C were synthesized at a temperature of 600 [DEGREE SIGN]C, while MLG was obtained at temperatures in excess of 800 [DEGREE SIGN]C. Schottky-junction solar cell devices prepared using films produced at 400 [DEGREE SIGN]C, 600 [DEGREE SIGN]C, 800 [DEGREE SIGN]C, and 1,000 [DEGREE SIGN]C coupled with n-type Si demonstrate power conversion efficiencies of 0.003%, 0.256%, 0.391%, and 0.586%, respectively. A HNO3 treatment has further improved the efficiencies of the corresponding devices to 0.004%, 1.080%, 0.800%, and 0.820%, respectively. These films are promising materials for application in low-cost and simple carbon-based solar cells.     

Preparation of conducting polyacrylonitrile/polypyrrole composite films by electrochemical synthesis and their electrical properties

Electrically conducting polyacrylonitrile (PAN)/polypyrrole (PPy) composite films were prepared by electrochemical polymerization of pyrrole in an insulating PAN matrix under various polymerization conditions and their electrical properties were studied. The conductivities of PAN/PPy composite films peeled off from the platinum electrode he lie in the range of 10^?2–10^?3 s/cm, depending on the preparation conditions: The conductivity increased with the concentrations of the electrolyte and the monomer, but it decreased with the polymerization temperature of pyrrole and the applied potential.     

Ionic conductivity in crosslinked poly(β-cyanoethylmethylsiloxane) network films containing lithium perchlorate

Summary Polymeric solid electrolytes with high ionic conductivity, excellent mechanical strenght and flexibility were prepared by dispersing homogeneously lithium perchlorate in the crosslinked poly(-cyanoethylmethylsiloxane) and poly(-cyanoethylmethylsiloxane-co-dimethylsiloxane) network films. The ionic conductivity of the network films was close to 10^–5 Scm^–1 at room temperature and affected by the content of cyanoethylmethylsiloxane unit in the copolymers and the species and content of the crosslinking agents.     

Ionic conductivity of polyelectrolyte derivatives of poly(vinyl alcohol)-lithium ion complex films

Summary Ionic conductivity of various polymeric hybrid complexes made from the polyelectrolytes carboxymethylated poly(vinyl alcohol) (PVAC), poly(vinyl alcohol) acetalized with glyoxylic acid (PVAG) and poly(vinyl alcohol) acetalized with iodine N-methyl-4-pyridyladehyde (PVAP) were investigated. It was found that when the content of carboxyl group in PVAC reaches 5.3% and the content of carboxyl group in PVAG is more than 9.7%, the ion conductivity of polymeric hybrid complexes rises sharply. These polymer—Li⁺ complex hybrids gave the ionic conductivity of 10^–6 Scm^–1 at room temperature.     

Ionic conductivity in mixtures of salts with comb-shaped polymers based on ethylene oxide macromers

A comb-shaped polymer was prepared from a vinyl ether monomer comprising three oxyethylene units with a terminal methoxy group. The polymer could dissolve LiClO₄, NaClO₄, and LiSO₃CF₃ salts to form homogeneous amorphous mixtures, and the glass transition temperatures in each system were observed to increase with added salt. A.c. conductivity studies on the mixtures of polymer-LiClO₄ showed a dependence on both salt concentration and temperature. Room temperature conductivities were around 10^?5Scm^?1 rising to about 10^?3Scm^?1 at ～ 380K. A maximum in the conductivity was detected which altered with temperature. Conductivities which displayed non-Arrhenius behaviour were analysed using the Vogel-Tammann-Fulcher equation and interpreted on the basis of the configurational entropy model derived by Gibbs and coworkers.     

Thermal stability studies of transparent conducting polyaniline composite films on their conductivity and optical spectra

The thermal stability of highly transparent and conducting polyaniline–Nylon 6 (PAn-N) composites films doped with various protonic acids such as hydrochloric acid (HCI), benzenesulfonic acid (BSA), sulfosalicylic acid (SSA), and p-toluenesulfonic acid (TSA) was investigated at different elevated temperatures under air atmosphere. Two different degradation kinetic processes of electrical conductivity were found depending on the species of protonic acids. The conductivity degradation of PAn-N composite films doped with SSA and TSA were found to obey first-order reaction kinetics, while that of the other dopants was found to follow multiorder kinetics. Spectroscopic studies revealed that the thermal de-doping process of doped composite films, which reversed the doping process, took place without major structural modifications of the polyaniline in the composite system but was not completely reversible. From the differential scanning calorimetry (DSC) study, the crystal structure of the composite films was found to be affected by the formation of polyaniline in matrix polymer and depended on the types of dopant species. © 1995 John Wiley & Sons, Inc.     

Synthesis and conductivity of proton-electrolyte membranes based on hybrid inorganic–organic copolymers

A class of new proton-electrolyte membranes (PEM) based on inorganic–organic copolymers were synthesized from 3-glycidoxypropyltrimethoxysilane (GPTS), sulfonated phenyltriethoxysilane (SPS), tetraethoxysilane (TEOS) and H₃PO₄. Their thermal stability, microstructure, and proton conductivity were investigated under the conditions for PEM fuel cell operation. TGA–DSC analysis indicated that these membranes are thermally stable up to 180 °C. Scanning electron microscope (SEM) micrographs show that the membranes are dense. A proton conductivity of 1.6×10⁻³ S/cm was observed at 100 °C in a dry atmosphere for a sample with 0.5 mol GPTS and 1 mol H₃PO₄ in 1 mol Si, representing the highest proton conductivity in anhydrous state among PEMs ever reported. In an environment with 15% relative humidity (RH), the proton conductivity increased to 3.6×10⁻² S/cm at 120 °C. The proton conductivity increases with H₃PO₄ contents and relative humidity. The hybrid inorganic–organic materials can be readily fabricated in membrane form with thickness as thin as 20 μm on porous electrodes; they have great potential to be used as the electrolytes for high-temperature PEM fuel cells.     

Piezoelectric thick films and their application in MEMS

Piezoelectric thick films (up to 10 μm thick) and piezoelectric micromachined ultrasonic transducer (pMUT) have been successfully demonstrated at low temperatures of 650 °C using a composite thick film processing route. Submicron-sized PZT powder was dispersed into sol–gel solution to form homogeneous slurry for spin-coating on silicon substrate. Issues associated with recipe of the slurry, deposition process and sintering of films have been summarized with a view to optimizing the properties of the films and pMUTs. Typical microstructure, ferroelectric and piezoelectric properties of the composite films are given. Thermal stability of bottom electrode, a key issue about device fabrication, has also been investigated. The ultrasound-radiating performance of the pMUT element in response to a continuous alternating current driving voltage has been reported. The generated sound pressure level is 116.8 dB at 76.3 kHz at a measuring distance of 12 mm. The pMUT is suitable for application of airborne object recognition.     

Review on adhesive joints and their application in hybrid composite structures

Composites have been used extensively in various engineering applications including automotive, aerospace, and building industries. Hybrid composites made from two or more different reinforcements show enhanced mechanical properties required for advanced engineering applications. Several issues in composites were resolved during the last few years through the development of new materials, new methods and models for hybrid joints. Many components in automobile are joined together either by permanent or temporary fastener such as rivets, welding joint and adhesively bonded joints. Increasing use of bonded structures is envisaged for reducing fastener count and riveted joints and there by drastically reducing assembly cost. Adhesive bonding has been applied successfully in many technologies. In this paper, scientific work on adhesively bonded composites and hybrid composites are reviewed and discussed. Several parameters such as surface treatment, joint configuration, material properties, geometric parameters, failure modes, etc. that affect the performance of adhesive bonded joints are discussed. Environmental factors like pre-bond moisture and temperature, method of adhesive application are also cited in detail. A specific case of adhesive joints in hybrid bonded-bolted joints is elaborated. As new applications are expanding in the field of composites joining and adhesive joints, it is imperative to use information on multiple adhesives and their behaviour in different environmental conditions to develop improved adhesive joint structure in mechanical applications.